Thermoset urea-formaldehyde (UF) resins are commonly used as binders for fiber reinforced composites because of their suitability for various applications and their relatively low cost. However, fiber reinforced composites bonded with neat UF resin are often brittle and cause processing and product performance issues. In order to overcome these issues, it is common to modify UF resin with conventional latexes, such as polyvinyl acetate, vinyl acrylic, or styrene-butadiene latexes. Modifying UF resin with conventional latexes improves the flexibility of fiber reinforced composites which in turn improves the strength of fiber reinforced composites. Improved strength is needed to achieve high speed processing of fiber reinforced composites on commercial manufacturing lines as well as optimal product performance. However, these conventional latex modifiers are typically expensive and the modification of UF resins with conventional latexes increases binder cost significantly. In addition, conventional latexes are petroleum-based, and are thus derived from a non-renewable and non-sustainable resource. Therefore, there is a need to develop binder compositions that are more cost effective, more environmentally sustainable, and that do not degrade the strength of fiber reinforced composites.